Discharge tube



Jan. 26, 193 7.

o. STETTLER DISCHARGE TUBE Filed Dec. 8, 1933 2 Sheets-Sheet 1 Jhvenlor.

if I

Jan. 26, 1937.

0. STETTLER 2,068,775

DISCHARGE TUBE Filed Dec. 8, 1935 2 Sheets-Sheet 2 w mm .5

Patented Jan. 26, 1937 UNITED STATES PATENT OFFICE Application December8, 1933, Serial No. 701,503 In Switzerland December 21, 1932 11 Ciaims.

This invention relates to the control of the electron current in anelectron tube especially for the purposes of current regulation,amplification, rectification, conversion and the like.

It has been proposed heretofore to control the electron current byregulating the cross-sectional area of the current path. Due to thepeculiarities of the electron stream, however, and the fact that thestream contracts with increasing current, this manner of control is notsusceptible to fine regulations. Furthermore, in a gaseous electron tubewherein the discharge current is set up mainly by vapor ions, startingand stopping the discharge ordinarily cannot be accomplished.

It is an object of the present invention to regulate the electroncurrent in a more accurate and closer manner than has been possibleheretofore by regulating, not the cross-sectional area of the electronstream, but the extent of active area of the electrodes, or at least oneof them, that forms a seat for the stream. The electron current is afunction of the active area and hence by varying the active area and byproper shaping of the screen or electrode area, or both, fine regulationand control in accordance with any selected plan may be accomplished.Further, by completely eliminating all active area of an electrode fromthe electron stream, the discharge ceases. Hence the discharge can bestarted and stopped at will.

A further object is in regulating the extent of effective active area ofa working electrode of an electron tube by a screen which is movableacross the active area, and is positioned so closely thereto that thescreened area is excluded from the electron stream. For control of theelectron stream it is essential that there be relative movement betweenthe screen and electrode. It is immaterial which is the movable memberalthough for practical purposes it is preferable that the screen be themovable member.

A further object is the provision of an electron tube having twoelectrodes, as two anodes, and a third electrode, as a cathode, commonto the first two electrodes, with a screen so arranged as alternately tocontrol the discharge streams between the common electrode and the twoelectrodes so that, for instance, the conversion of direct intoalternating current can be'eifected.

It is a further object to mount the control screen on a vibratilesupport. The natural periodicity of vibration is about equal to thedesired periodicity of control of the electron stream so that the screencan be vibrated electromagnetically by a small amount of alternatingcurrent energy of approximately the same periodicity, and the amplitudeof vibration can be modified by small changes of periodicity of theactuating current.

As in highly evacuated tubes with a filament the magnitude of theemission, among other things, constitutes a function of the size of theactive emission surface, it is possible in certain cases to arrange themovable screening member directly in front of the active cathode surfacewhereby there is again possible the advantage of a fine stage regulationof the discharge. Such arrangement constitutes a further object of theinvention.

The movement of the member by means of 15 which the emission iscontrolled may be effected by positive control, it may, for alternatingcurrent rectifying, direct current conversion into alternating currentand relay purposes with relatively large time constants, be a mechanicalsine shaped oscillation, while there is utilized the advantage that forthe energization and maintenance of a mechanical oscillation in thenatural frequency of the oscillating body, particularly when this issuitably constructed, a very small amount of energy is required. This isa further object of the invention.

For relay, alternating current rectifying or direct current convertingtubes, which operate with gas discharges, the arrangement, according tothe invention, enables the stationary and movable screening elements, inspecial cases the movable anode or cathode, to be so constructed thatwhen the movable member is in the position of rest the anode space is soseparated from the cathode space that the discharge along a path otherthan the usual one is obviated. This arrangement is a further object ofthe invention.

Examples of construction according to the subject of the invention areillustrated in the accompanying drawings, wherein:

Fig. 1 shows in diagrammatic section a first form of construction of adischarge tube as relay.

Fig. 2 shows the resonance curve of the spring thereof.

Fig. 3 shows a form of construction of a discharge tube as a doubleresonance relay in perspective View, and

Fig, 4 the circuit diagram thereof.

Fig. 5 shows in diagrammatic section a further form of construction of adischarge tube for the conversion of direct current into alternatingcurrent, or alternating current into direct current.

Fig. 6 shows in vertical section a form of construction of a dischargetube for converting dh'ect current into polyphase current or polyphasecurrent into direct current, and

Fig. '7 shows a diagrammatic plan thereof.

Fig. 1 shows a discharge tube of high vacuum or with gas filling, ofwhich the glass bulb I is secured in the usual manner on a base 2. Onthe base there is secured, inside the bulb, a magnet 3 of which the core4 carries the winding 5. To the foot of the magnet 3 an upwardlyextending spring 6 is so secured that it swings to and fro in responseto variations of energization of said magnet. The spring carries at theupper end a screen plate i of metal or insulating material which coversa correspondingly large opening of a box-shaped screen casing 8 of metalor insulating material.

The screening and also the spring can be connected to a suitablepotential through high ohmic resistances for keeping the potentialconstant. In the interior of the screen casing 8 is located theelectrode 9 which has a surface thereof, projecting into the openingthereof. Outside the screen casing 8 there are located directlyunderneath, the counter electrodes ID, in this case anodes. When apotential, for example the continuous voltage of the battery B, isapplied to the stationary electrodes a discharge current is produced assoon as the screen plate 1 exposes the opening of the casing 8. Theactive cathode surface varies according to the size of the opening thusexposed and thus also the strength of the discharge current. When themagnetic flux is varied, for example, by a variable direct current themovable screen part can be moved thereby more or less from its restposition, While the size of the active electrode surface is varied. Themovement of the spring may be effected by mechanical, magnetic,electromagnetic, electrodynamic or other forces.

The advantage of this arrangement resides in the fact that by means of avery small controlling energy large energies, which traverse thedischarge path, can be varied continuously and in proportion to thecontrolling energy. When the control electrode is so constructed that ithas a low mechanical inertia, this relay may be employed, when using agas discharge, preferably as amplifier for acoustic frequency mixtures.With such a tube it is possible with a small control energy and whileusing a low anode potential, to obtain a larger controlled output thanwith the arrangements at present known. As it is possible to suitablyarrange the ratio of the discharge current, relatively to the controlcurrent, in other words to suitably shape the static and thus also thedynamic base lines, on the one hand by suitably shaping the coveringopenings and on the other hand by varying the rectifying force of theelectrode, the distortions occurring in a preceding amplifier part or ina loud speaker can be corrected by a tube of this character.

As a continuously adjustable relay for controlling operations below theaudible frequency the tube described is particularly eflicient when theoscillating screen part according to Fig. 1 or a movable electrode isformed as a blade spring, while it is particularly of importance thatthe spring has a sharply defined natural frequency and the energyrequired for maintaining the oscillation is small.

When an alternating current is used as controlling current, which can bevaried in the frequency range I (Fig. 2) the amplitude of the springfrom zero to maximum according to the resonance curve (Fig. 2) of thespring can be obtained by the frequency variation f.

In the electrical transmission technology there frequently arises thenecessity of transmitting continually varying operations by wire or byWireless and in the general art it is frequently desirable to transmitmovement operations in finely adjusted form and staging by means ofdistant transmission. The combined problem, formed by these twoproblems, of electrical transmission was solved hitherto by means ofmore or less complicated devices which were exposed to numerous sourcesof error and were therefore only relatively reliable. he problem inquestion can be solved with advantage by the arrangement hereinafterdescribed.

As is well known, only very small energies are required for oscillatinga body which is easily capable of oscillation when the drivingalternating force has a frequency in the neighbourhood of the naturalfrequency of the body. The transmission ratio of the relay in thisarrangement is therefore particularly large.

It will be understood by the mounting of a number of springs havingdifferent natural frequencies in a tube it is possible to transmitdifferent control operations which are continuously adjustableindependently of one another. The controlling current must then be afrequency mixture which is composed of the variable alternating currentsof frequency ranges of the springs which have been provided. Thiscomposite controlling frequency can best be produced on the control sideby one or more tube oscillators, while for tuning there are usedadjustable oscillating circuits. Each oscillating circuit must in thiscase include the frequency range of at least one spring.

Fig. 3 shows in perspective View a gas discharge relay wherein the sizeof the active anode surface 1 is varied for regulating the strength ofdischarge. As in the constructional form described all the partsincluding the glass bulb l are secured in a gastight manner on a base 2.To the base is secured a permanent magnet 3 with O-shaped magnet body,at the sides of the limbs of which are provided short cores which carrytwo coils 5. Opposite the pole faces of these cores two blade springs 5are secured at their lower ends for free oscillation to the magnet yoke.These two springs have different natural frequency numbers which deviateby about 10% from the average control frequency. One spring. forexample, has a natural frequency of Lil-5:45 cycles, the other 50+5=55cycles. To the free ends are secured at right angles to the springsurface anodes formed as transv'mse plates 3', which during oscillationenter slots of metal screens 8 provided on both sides. On both sides ofthis screening there are provided outside thereof filaments 9 which arecarried by holders 2! serving simultaneously for the supply of current.As the screening plates are also mounted on these holders there ispractically no potential difference between them and the filam nts. Thetwo coil ends, the filament outgoing wires and the springs areelectrically insulated from one another and are connected to the crresponding base pins and the glass bulb is filled with a gas suitablefor ionization.

Fig. 4 shows diagrammatically the circuit of a tube of this characterand at the same time an example of use for the production of acontinuous control movement. The two anodes '5 are in this caseconnected to the outer ends of a two part solenoid S of which the middlepoint is connected to any suitable source of current. A forked armatureA, mounted on a shaft, engages with its prongs in the two solenoid coilsand is rocked in one or the other of the coils according to theamplification of the current. On the armature shaft may be mounted, forexample, the valve body of a controlling valve for a hydraulic orpneumatic servomotor.

The method of operation of this device is as follows: The current froman amplifier flows modulated in control frequency through the two magnetcoils 5, so that the permanent magnetism is amplified or weakened in thesame rhythm as the current fluctuations. If now, by means of the controlmember of the transmitting device, the control frequency is alwaysapproached more towards the natural frequency of one of the springs 6this acquires gradually stronger vibrations, i. e. resonance, the moreit approaches the natural frequency. The anode plate '5 of theoscillating spring passes with an always increasing amplitude on bothsides through the corresponding screen slots and when a positivepotential is applied to the anode l relatively to the filaments 9 thereoccurs at each passage of the plate I through the screen slot a powerfultransmission of current between plate 1 and filament 9.

The occurring current is approximately proportional to the plate surfacepassing through, this in turn being proportional to the oscillationamplitude. The amplitude increases with increasing approach of thenatural frequency of the control frequency towards the natural frequencyof the spring. This approach is effected by suitable movements of thecontrol member at the transmitting station from the zero positionoutwardly. By suitably shaping the oscillating anode plates 1proportionality can be obtained between the angle of movement of thecontrol member and the control movement. When the control member ismoved from the zero position towards the other side the same actiontakes place by the other spring. This effects a control movement towardsthe other side.

By means of the double resonance relay it is possible to adjust controlmovements to the left and right through a suitable angle with greatrapidity and precision. The control operation is not effected in stages,but continuously, which is essential for the precision of the control.This resonance distant control takes place with a minimum of electrontubes. It is therefore, by reason of its simplicity, also very reliable.It will be readily understood that by suitably increasing the number ofsprings in the relay the various controls can be actuatedsimultaneously.

The discharge relay for high vacuum or gas filling above described canalso be used with advantage as frequency generator. Electric frequencygenerators, which mostly operate with back coupled electron tubes,depend upon a number of working conditions, for example on the anodepotential, the grid potential, the heating potential, the guiding of theleads, on the temperature and so forth. From this it follows that theproduction of a constant frequency by this method is very difficult.Quartz oscillators are particularly suitable for high frequencyoscillations. The frequency generator according to the arrangement abovedescribed is characterized by its great frequency constancy asmechanical oscillatory structures with prominent natural frequency arevery uniform in frequency at constant temperature. The resonance curveis very steep. The steepness thereof is further increased because in thearrangement described the oscillatory structure operates in vacuum or atconsiderably reduced pressure. For the production of high frequencythere may be used the known means of frequency multiplication. Themaintenance of the oscillation may be effected by the controlledcurrent. For the production of a number of constant frequencies a numberof oscillating systems may be mounted in a tube. For the production of avariable fequency the securing point of the oscillatory structure may bevaried by a suitable device.

While the discharge tube relay serves for the continuous linear ornon-linear output amplification of comparatively slow control operationsas also for the production of qonstant frequencies such a tube may alsobe used as an undulator of suitable currents or particularly for theconversion of continuous current into alternating current of suitableform of the current or potential wave and suitable phase number.

Fig. 5 shows the simplest form of arrangement for the conversion ofcontinuous current into alternating current by means of a discharge tubeof this character. A glass bulb I, highly evacuated, or filled withdilute gas, which has suitable properties for the discharge operations,is secured to the base 2. A magnet system 3, which can be variouslymagnetized by the coil 5 fitted on the core 4, carries the blade spring6 consisting of magnetic material. The screening casing 8 of metal orinsulating material with the central portion 8a. and the two dischargeopenings 82) contains in each of the two chambers, formed by thepartition 8a, an anode l which-anodes are seated directly adjacent theopenings 81) and are connected each to a separate end of the primarywinding of the associated transformer T. The middle tapping of thiswinding leads to the positive pole of the direct current source B. Acover plate I, which in the rest position covers the openings 81), issecured to the upper end of the blade spring 6. Outside the screeningcasing 8 is provided the counter electrode 9. The cathode 9 is connectedto the negative pole of the direct current source B. The naturalfrequency of the spring is so chosen that it coincides with thealternating potential to be produced. The magnet winding may beconnected to the secondary winding of the transformer T. When the spring6 is oscillated by an alternating current passing through the coil 5 thetwo discharge openings to. and 8b are alternately exposed, the dischargecurrent alternately following the path, in the manner of a simplecommutator, between one of the two anodes l0 and the cathode 9. Bysuitably shaping the discharge openings the curve of the alternatingcurrent may be given any suitable shape. By the use of an indirectlyheated cathode, as shown the whole of the direct current potential maybe utilized for heating.

By means of a direct current winding, which is superposed on the winding5, not necessarily illustrated, the spring initially may be rocked bythe switching-in current impulse. The natural frequency of the springthus determines the frequency of the alternating current produced. Whenthe tube is adapted for the additional feeding on alternating currentmains already under voltage the control of the spring must be efiectedpositively from the mains which can be effected in a simple manner.

An alternating current rectifier of the construction described may alsobe used in a suitable manner as continuous current converter preferablyfor high voltages, as by the mechanical closing of the discharge paththe danger of a back fire can be obviated to a far-reaching extent.

Instead of a control element with a reciprocating oscillatory movement,such as spring 6, there may also be used a control member with a rotarymovement. The rotary movement thereof may be produced by means of amagnetic rotary field of which the energizing winding is located outsidethe bulb of the discharge tube. By means of a rotary system of thischaracter transforming undulations of diiferent types can be obtained.

In Figs. 6 and 7 is shown such an arrangement with the use of doublecommutation for converting direct current into alternating current orpolyphase current into direct current. On a base 2 there is again fitteda glass bulb I. As a movable part of the screening there serves a rotaryhollow cylinder or rotor 17. When the rotary movement has a speed of3000 revolutions per minute (for producing 50 cycles) there is providedin each upper part of the rotor I? a slot 17a of peripheral length orwidth and both slots are arranged diametrically opposite one another sothat in the drawing only the upper one is visible. At the upper andlower ends the hollow cylinder I! is closed. At the upper end of therotor is a two pole armature l8 of magnetic steel which is rotated by arotary field, produced by a winding H) (for polyphase current or singlephase alternating current) surrounchng the bulb on the outside. To thebase 2 is secured centrally a shaft 29 on which the rotor rests by anupper pivot bearing and is guided by a bore in a central partition iii).In the upper rotor chamher an anode 22 of graphite is arranged on theshaft 26. In the lower rotor chamber is fitted an indirectly heatedcathode 23. The current lead 26 of, the central electrode 22 passesthrough a longitudinal bore of the shaft 20 to the anode. The rotor H issurrounded by a stationary part or stator, which is formed by threeuniformly spaced casing sectors 25 provided on the periphery. Each ofthese Casing sectors receives in its upper part an indirectly heatedcathode 2B and in its lower part an anode 21 which closes the saidopening of the sector. The cathode and anode of each casing sector areconnected together conductively and their leads are passed vithinsulation through the wall of the casing sector. To each anode-cathodepair is connected a three phase current lead I, II, III as shown in Fig.'7. The positive pole of the battery B is connected to the central anode22 and the negative pole of the former to the central cathode 23. Inthis arrangement a three phase current of the usual type is produced inthe three phase system D by three single phase currents relativelydisplaced by The sine shape of the alternating current produced may inthis case also be produced by suitable construction of the laterallimiting edge of. the rotor slots.

When additionally feeding three phase mains already under voltage withsuch a discharge device the rotary field for the rotor drive ispreferably produced by the current taken from the three phase mains andan entire phase uniformity can be obtained in this case by the rotaryarrangement of the rotary field winding and its adjustment. When feedingthree phase mains not otherwise excited at a governed frequency thefrequency constancy can be obtained by obtaining the rotary field, forexample by means of a discharge device with a pendulum control of thetype of the discharge tubes hereinbefore described of, which the magnetis provided with a main and a phase displaced auxiliary winding.

Devices for converting direct current into alternating and three phasecurrent by this arrangement are characterized by their great simplicityand security in operation, do not sufier from spark formation, oxidationor burning of the active parts, have no dimensions and a low weight andrequire no attention. It is also possible to suitably influence theshape of curve of the alternating current produced. Such converters andrelay discharge tubes can also be produced in small units witheconomical methods of operation.

In the examples described with movable electrode the anode is arrangedto oscillate, the cathode could also be arranged to oscillate equallywell.

I claim:

1. A discharge tube comprising an anode and a cathode between which adischarge is adapted to take place, and movable means mounted closelyadjacent one of said electrodes for varying the eifective dischargesurface area of the adjacent electrode from which the discharge takesplace.

2. A discharge tube comprising an anode and cathode, a movable anodescreening member located between said anode and cathode and closelyadjacent to the active face of said anode to exclude the adjacent partthereof from the discharge, a movable support on which said member ismounted, and means for actuating said support whereby said screeningmember is moved relatively to said anode and cathode to vary theeffective area of said anode.

3. A discharge tube comprising a base, a glass bulb on said base, anelectromagnet mounted on said base inside said bulb, a housing in saidbulb, said housing having an aperture therein, a cathode located in saidhousing adjacent said aperture, 9. pair of anodes in said bulb, aresilient support mounted in said base on said bulb, and a screen membercarried by said support and extending between said cathode and saidanodes.

4. A discharge tube comprising an anode and cathode, a movable screeningmember located between said anode and cathode and closely adjacent oneof them to exclude the adjacent part of the electrode from the dischargebetween said anode and cathode, a resilient support on which said memberis mounted, electromagnetic means for actuating said resilient supportwhereby said member is moved relatively to said anode and cathode tovary the extent of screened electrode surface, said movable member beingadapted to be oscillated by energizing the electromagnetic means by thealternating current that is independent of the anode-cathode current,the average strength of the discharge being a function of the amplitudeof oscillation of the movable member, while the magnitude of the amplitude of oscillation is a function of the output of the controllingalternating current of constant frequency.

5. A discharge tube comprising a base, a glass bulb on said base, andelectrcmagnet mounted on said base inside said bulb, a housing in saidbulb, said housing having an aperture therein,

a cathode located in said housing adjacent said aperture, a pair ofanodes in said bulb, a resilient support mounted in said bulb, and adischarge-controlling screening member carried by said support betweensaid cathode and said anodes and movable alternately to control theseparate discharge paths between said anodes and said cathodes.

6. A discharge tube comprising a base, a glass bulb on said base, anelectromagnet mounted on said base inside said bulb, a housing in saidbulb, said housing having an aperture therein, a cathode located in saidhousing adjacent said aperture, a pair of anodes in said bulb, aresilient support mounted in said base in said bulb, and a screeningmember carried by said support and adapted to extend between saidcathode and said anodes, and means for vibrating said support to movesaid screening member into controlling position between said cathode andalternately between said anodes.

7. A discharge tube comprising a base, an evacuated bulb on said base, apermanent magnet with U-shaped body on said base, short cores on thelimbs of said magnet, coils on said cores, blade springs confrontingsaid cores and attracted thereby, said blade springs having difierentnatural frequencies of oscillation, anodes in the form of plates securedto the free ends of said springs, screens having slots therein mountedin said bulb, said anodes being movable through said slots, holders onsaid base, and filaments supported by said holders, said holders alsosupporting said screens which are located between the filaments and theanodes.

8. An electron tube having a pair of cooperating electrodes betweenwhich an electron current may pass, means for varying the active area ofone of said electrodes including a control screen closely adjacent saidone electrode to exclude the adjacent screened surface thereof from thedischarge between said electrodes, and means for efiecting relativemovement between said one electrode and screen for varying the extent ofscreened electrode surface.

9. An electron tube having a pair of cooperating electrodes betweenwhich an electron current may pass, means for varying the electroncurrent comprising a housing surrounding one of said electrodes havingan opening occupied by an active face of said one electrode, and ascreen member movable across said opening and also across and closelyadjacent to the active face of said one electrode to isolate thescreened part of the active face thereof from the current path betweensaid electrodes.

10. An electron tube having a cathode and a pair of anodes, and movablescreening means closely adjacent the active areas of said anodes toexclude theadjacent screened areas from the discharge path between saidanode and cathode and movable relatively thereto for alternately varyingthe efiective areas of said anodes.

11. A discharge tube comprising a cathode and anode, a movable screeningmember located between said cathode and said anode and closely adjacentone of them to isolate the adjacent area thereof from the dischargepath, and means for relatively moving said member and screened electrodeto vary the effective surface area of the electrode that is exposed tothe discharge betwen said cathode and anode.

' OSCAR STET'ILER.

